The prefabrication, erection, maintenance and dismantling of working structures such as off-shore, and on-land workover oil drilling and exploration platforms, as well as the erection of permanent multi-floor buildings and other engineered structures have problems in common. It is an object of this invention to preserve both new and existant building structures and like frameworks, through the application of tension applied through hydraulic translation. Fabrication is of course primary, while life expectancy of the structure is commensurate with the subjection to external forces that have deteriorating effects. Transport of structural members to the erection or building site in a disassembled condition is advantageous, and adverse conditions are expected to be encountered at the site. Not only are there irregularities in the geological formations relied upon for foundation support, but there are irratic dynamic forces applied in the form of wind and ocean waves, and shifting earth formations as well. The steady application of external forces is one factor to be accounted for, and the frequency of wave application of forces is a second factor to be accounted for. An object therefore, is the partial or complete absorbtion of energy entering the structure by means of controlled hydraulic damping.
A characteristic of any structure is its mass inertia and inherent resonant frequency, to be considered with respect to the frequency of externally applied wave motion forces. Rigid structures, although to an extent resilient, eventually fail as they are continuously subjected to stresses and strains that result in fatigue. It is the flexure and bending of columns and trusses under load condition, members that are rigidly interconnected and eventually fail when repeated cycles of force applications cause fatigue at the critical points of joinder. Collapse is an eventuality. Accordingly, it is a general object of this invention to provide means by which structures comprised of floors and platforms are erected and dismantled at their sites, and utilizing internally pre-stressed tubular members under hydraulic pressure that is translated to support said floors and platforms under tension loading, all of which is flexible as distinguished from rigid and therefore not as readily subject to fatigue and subsequent failure.
Reference is made to U.S. Pat. No. 3,438,653 issued to the inventor herein on Nov. 10, 1970, entitled Hydraulic Structural Apparatus, wherein "translators" are disclosed for the purpose of hydraulically translating fluid pressure (by means of fluid transfer) created by the support of a floor slab and/or lateral thrusts to the interior of liquid column elements and structural columns in combination therewith. Said liquid column elements are embodied in multiple tubular members which are placed in tension through circumferential and axial prestress by the application of internal hydraulic pressure. These multiple tubular members are constrained within an envelope member, as a bundle of slender thin walled tubes, used as both primary support columns and as secondary tension members, with pressure equilibrium of the fluid within the columns determined by the said hydraulic translators used to restrain column end conditions. It is an object of this invention to advantageously employ the aforesaid prestressed multi tube structural members, for their high load capabilities and flexible properties independant of the floor or platform supported thereby.
The raising of prefabricated floors and platforms has been proposed and practiced in various forms, invariably however with their rigid interconnections to the supporting columns. On the contrary, it is an object herein to isolate and separate the mass of the platform from its supporting column and associated diagonal and/or horizontal bracing, and to this end I provide a suspension lift means carried from the head of the prestressed column. A feature or said lift means is its support by means of pressure translation at the head of the column, the support function thereof being independent of the lifting and lowering functions as later described.
The suspension lift means takes several forms as it is disclosed therein. A characteristic feature is the stepped-spool configuration of the secondary tensioned support members, providing a series of controlled sequenced elevations for floor and platform support. Another feature is the cable tension core of said secondary support member, the spools being arranged therealong and each swaged so as to be immovable therewith. Further, hydraulically operable slip-clamps are employed to disengageably rest upon the spools which provide incrementally elevated steps therefor. In its simplest form the lift means is single acting to incrementally raise the floor, permitting it to be lowered by gravity. However, in the form shown the lift means is double acting to drive the platform both upwardly and downwardly.
Buildings, and particularly high-rise structures and similarly on-land or on-shore workover and off-shore rigs for the exploration and production of oil are subjected to vibrations as a result of severe wind loads, and the latter to the hydraulic action of the seas. These are exterior forces that are applied on a continuing basis with fluctuations ever present in complex wave form, also applied as impact forces at times. Reference is made to relatively constant wind and ocean wave motions on the one hand, and to seismic movements of the earth and tidal waves on the other hand. As external force in various forms of wave energy are applied to building structures, increased and reduced loads are applied to interrelated members, with detrimental stress increases. With the multi-tube hydraulic tensioned support employed herein such loads are taken into the heavily loaded hydraulic columns and translated through controlling orifices to secondary members, to restrain oscillation when the initial load application is released. It is an object therefore to hydraulically damp the prestressed structure, so as to absorb high energy external force application and to dissipate the same when the initial force is released.